Improved Plasmonic Filter, Ultra-Compact Demultiplexer, and Splitter

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  • ABSTRACT

    In this paper, metal insulator metal (MIM) plasmonic slot cavity narrow band-pass filters (NBPFs) are studied. The metal and dielectric of the structures are silver (Ag) and air, respectively. To improve the quality factor and attenuation range, two novel NBPFs based on tapered structures and double cavity systems are proposed and numerically analyzed by using the two-dimensional (2-D) finite difference time domain (FDTD) method. The impact of different parameters on the transmission spectrum is scrutinized. We have shown that increasing the cavities’ lengths increases the resonance wavelength in a linear relationship, and also increases the quality factor, and simultaneously the attenuation of the wave transmitted through the cavities. Furthermore, increasing the slope of tapers of the input and output waveguides decreases attenuation of the wave transmitted through the waveguide, but simultaneously decreases the quality factor, hence there should be a trade-off between loss and quality factor. However, the idea of adding tapers to the waveguides’ discontinuities of the simple structure helps us to improve the device total performance, such as quality factor for the single cavity and attenuation range for the double cavity. According to the proposed NBPFs, two, three, and four-port power splitters functioning at 1320 nm and novel ultra-compact two-wavelength and triple-wavelength demultiplexers in the range of 1300-1550 nm are proposed and the impacts of different parameters on their performances are numerically investigated. The idea of using tapered waveguides at the structure discontinuities facilitates the design of ultra-compact demultiplexers and splitters.


  • KEYWORD

    Metal-insulator-metal (MIM) waveguide , Optical multiplexer , Optical splitter , Optical plasmonic filter , Nanodisk resonator

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  • [TABLE 1.] Parameters of the Drude-Lorentz model for silver [25]
    Parameters of the Drude-Lorentz model for silver [25]
  • [FIG. 1.] (a) Schematic view of a single in-line slot cavity narrow band-pass filter (NBPF) structure. (b) Comparison of analytical and numerical resonance wavelengths. (c) Quality factor and spectrum peak values vs. the cavity length L, assuming di=do=100 nm, W=180 nm, and G= 16 nm. (d) Variations of the peak of the transmission spectra for three different values of the metallic gap sizes, G, assuming L=564 nm, d=100 nm, and W=180 nm. (e) Quality factor and spectra peak values vs. metallic gap size, G, assuming L=564 nm, di=do=100 nm, and W=180 nm.
    (a) Schematic view of a single in-line slot cavity narrow band-pass filter (NBPF) structure. (b) Comparison of analytical and numerical resonance wavelengths. (c) Quality factor and spectrum peak values vs. the cavity length L, assuming di=do=100 nm, W=180 nm, and G= 16 nm. (d) Variations of the peak of the transmission spectra for three different values of the metallic gap sizes, G, assuming L=564 nm, d=100 nm, and W=180 nm. (e) Quality factor and spectra peak values vs. metallic gap size, G, assuming L=564 nm, di=do=100 nm, and W=180 nm.
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  • [TABLE 2.] Simulated specifications of the single cavity NBPF of FIG. 1
    Simulated specifications of the single cavity NBPF of FIG. 1
  • [FIG. 2.] (a) Schematic view of the single cavity NBPF with tapered waveguides. Specifications of the single cavity NBPF with tapered waveguides. (b) Comparison of analytical and numerical resonance wavelengths. (c) Quality factor and spectra peak values vs. cavity length, L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, and Si = So = 0.3. (d) Variations of the peak of the transmission spectra for four different values of the metallic gap sizes, G, assuming L = 524 nm, d = 100 nm, W = 180 nm and Si = So = 0.3. (e) Quality factor and spectra peak values vs. metallic gap size, G, assuming L = 524 nm, di = do = 100 nm, W = 180 nm and Si = So = 0.3. (f) Quality factor and spectra peak values vs. taper slope, S, assuming L = 524 nm, d = 100 nm, W = 180 nm, G = 16 nm.
    (a) Schematic view of the single cavity NBPF with tapered waveguides. Specifications of the single cavity NBPF with tapered waveguides. (b) Comparison of analytical and numerical resonance wavelengths. (c) Quality factor and spectra peak values vs. cavity length, L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, and Si = So = 0.3. (d) Variations of the peak of the transmission spectra for four different values of the metallic gap sizes, G, assuming L = 524 nm, d = 100 nm, W = 180 nm and Si = So = 0.3. (e) Quality factor and spectra peak values vs. metallic gap size, G, assuming L = 524 nm, di = do = 100 nm, W = 180 nm and Si = So = 0.3. (f) Quality factor and spectra peak values vs. taper slope, S, assuming L = 524 nm, d = 100 nm, W = 180 nm, G = 16 nm.
  • [FIG. 3.] Comparison of single cavity NBPF and tapered single cavity NBPF regarding quality factor and spectrum peak value. The straight lines are linear approximations of the data given.
    Comparison of single cavity NBPF and tapered single cavity NBPF regarding quality factor and spectrum peak value. The straight lines are linear approximations of the data given.
  • [TABLE 3.] Simulated specifications of the single cavity NBPF with tapered waveguides of FIG. 2
    Simulated specifications of the single cavity NBPF with tapered waveguides of FIG. 2
  • [FIG. 4.] (a) Schematic view of a double cavity NBPF, (b) its transmission spectra for three different values of the cavity length L, with di = do = 100 nm, W = 180 nm, G = 16 nm, and Gb = 44 nm.
    (a) Schematic view of a double cavity NBPF, (b) its transmission spectra for three different values of the cavity length L, with di = do = 100 nm, W = 180 nm, G = 16 nm, and Gb = 44 nm.
  • [FIG. 5.] (a) Schematic view of the double cavity NBPF with tapered waveguides. Specifications of the double cavity NBPF with tapered waveguides. (b) Variations of the peak of the transmission spectra for three different values of the cavity length L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, Gb = 44 nm, and Si = So = 0.3. (c) Comparison of analytical and numerical resonance wavelengths. (d) Quality factor and spectra peak values vs. cavity length L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, Gb = 44 nm, and Si = So = 0.3. (e) Quality factor and spectra peak values vs. the slope of the taper S, assuming di =do = 100 nm, L = 564 nm, W = 180 nm, G = 16 nm, and Gb = 44 nm. (f) Filter specifications, adapted from Matlab Simulink.
    (a) Schematic view of the double cavity NBPF with tapered waveguides. Specifications of the double cavity NBPF with tapered waveguides. (b) Variations of the peak of the transmission spectra for three different values of the cavity length L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, Gb = 44 nm, and Si = So = 0.3. (c) Comparison of analytical and numerical resonance wavelengths. (d) Quality factor and spectra peak values vs. cavity length L, assuming di = do = 100 nm, W = 180 nm, G = 16 nm, Gb = 44 nm, and Si = So = 0.3. (e) Quality factor and spectra peak values vs. the slope of the taper S, assuming di =do = 100 nm, L = 564 nm, W = 180 nm, G = 16 nm, and Gb = 44 nm. (f) Filter specifications, adapted from Matlab Simulink.
  • [TABLE 4.] Simulated specifications of double cavity NBPF with tapered waveguides
    Simulated specifications of double cavity NBPF with tapered waveguides
  • [FIG. 6.] Comparison of the frequency responses of single cavity NBPF (blue-dashed line), tapered single cavity NBPF (red-dotted line), double cavity NBPF (black-stripped line), and tapered double cavity NBPF (green line).
    Comparison of the frequency responses of single cavity NBPF (blue-dashed line), tapered single cavity NBPF (red-dotted line), double cavity NBPF (black-stripped line), and tapered double cavity NBPF (green line).
  • [FIG. 7.] Schematic view of the proposed two port power splitter structure, (b) its transmission spectra with L = 556 nm, W = 356 nm, G = 12 nm, di = do = 100 nm, Si = 2, and So = 0.5, and (c) transmission spectra for two different slopes of Sm. Magnetic field distributions for wavelengths of (c) 1320nm, demonstrate the splitting performance of the proposed device.
    Schematic view of the proposed two port power splitter structure, (b) its transmission spectra with L = 556 nm, W = 356 nm, G = 12 nm, di = do = 100 nm, Si = 2, and So = 0.5, and (c) transmission spectra for two different slopes of Sm. Magnetic field distributions for wavelengths of (c) 1320nm, demonstrate the splitting performance of the proposed device.
  • [FIG. 8.] (a) Schematic view of the proposed three port power splitter structure, and (b) its transmission spectra for L = 556 nm, W = 356 nm, G = 16 nm, di = 100 nm, do =56 nm, Si = 1, and So = 0.5. Magnetic field distributions for wavelengths of (c) 1320 nm, demonstrate the splitting performance of the proposed device.
    (a) Schematic view of the proposed three port power splitter structure, and (b) its transmission spectra for L = 556 nm, W = 356 nm, G = 16 nm, di = 100 nm, do =56 nm, Si = 1, and So = 0.5. Magnetic field distributions for wavelengths of (c) 1320 nm, demonstrate the splitting performance of the proposed device.
  • [FIG. 9.] (a) Schematic view of the proposed four port power splitter structure, and (b) its transmission spectra for L = 556 nm, W = 356 nm, G = 16 nm, di = 100 nm, do = 48 nm, Si = 1, and So = 0.5. Magnetic field distributions for wavelengths of (c) 1320 nm, demonstrate the splitting performance of the proposed device.
    (a) Schematic view of the proposed four port power splitter structure, and (b) its transmission spectra for L = 556 nm, W = 356 nm, G = 16 nm, di = 100 nm, do = 48 nm, Si = 1, and So = 0.5. Magnetic field distributions for wavelengths of (c) 1320 nm, demonstrate the splitting performance of the proposed device.
  • [FIG. 10.] (a) Schematic view of the proposed demultiplexer structure. Magnetic field distributions for wavelengths of (b) 1550 nm and (c) 1310 nm, demonstrate the demultiplexing performance of the proposed device. (d) its transmission spectra for two values of Si, for L1 = 628 nm, L2 = 524 nm, W1 = W2 = 164 nm, G = 16 nm, So=1, CD = 88 nm, and DL = 0.88 um. (e) Quality factor and spectrum peak value (SPV) of both channels, vs. input taper slope, Si, assuming waveguide width, di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, CD= 88 nm, So = 0.5. (f) Quality factor and spectrum peak value (SPV) of both channels, versus the distance between two cavity, CD, assuming waveguide width, di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, Si = 0.5 and So = 1. (g) Effects of L1 on quality factor and spectrum peak value (SPV) of both channels, assuming L2= 524 nm, waveguide width, di = do = 100 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, CD = 88 nm, Si = 0.5, So = 1. (h) Optimized two wavelength multiplexer for plasmonic dense wavelength division demultiplexing, the structure parameters are: W = 96 nm, di = do = 100 nm, L2 = 524 nm, L1 = 532 nm, G=16 nm, Si = 0.5, So = 1, CD = 120 nm.
    (a) Schematic view of the proposed demultiplexer structure. Magnetic field distributions for wavelengths of (b) 1550 nm and (c) 1310 nm, demonstrate the demultiplexing performance of the proposed device. (d) its transmission spectra for two values of Si, for L1 = 628 nm, L2 = 524 nm, W1 = W2 = 164 nm, G = 16 nm, So=1, CD = 88 nm, and DL = 0.88 um. (e) Quality factor and spectrum peak value (SPV) of both channels, vs. input taper slope, Si, assuming waveguide width, di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, CD= 88 nm, So = 0.5. (f) Quality factor and spectrum peak value (SPV) of both channels, versus the distance between two cavity, CD, assuming waveguide width, di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, Si = 0.5 and So = 1. (g) Effects of L1 on quality factor and spectrum peak value (SPV) of both channels, assuming L2= 524 nm, waveguide width, di = do = 100 nm, cavity widths of W1 = W2 = 164 nm, metallic gap size, G = 16 nm, CD = 88 nm, Si = 0.5, So = 1. (h) Optimized two wavelength multiplexer for plasmonic dense wavelength division demultiplexing, the structure parameters are: W = 96 nm, di = do = 100 nm, L2 = 524 nm, L1 = 532 nm, G=16 nm, Si = 0.5, So = 1, CD = 120 nm.
  • [TABLE 5.] Effect of changing output ports’ width, do, on filter specifications of two-port demultiplexer. Assuming: di = 100 nm, L1 = 628 nm, L2 = 524 nm, W1 = W2 = 164 nm, G = 16 nm, Si = 0.5 and So = 1, CD=88 nm
    Effect of changing output ports’ width, do, on filter specifications of two-port demultiplexer. Assuming: di = 100 nm, L1 = 628 nm, L2 = 524 nm, W1 = W2 = 164 nm, G = 16 nm, Si = 0.5 and So = 1, CD=88 nm
  • [TABLE 6.] Effect of cavities’ width, W=W1=W2, on filter specifications of two-port demultiplexer. Assuming: di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, G = 16 nm, Si = 0.5 and So = 1, CD = 88 nm
    Effect of cavities’ width, W=W1=W2, on filter specifications of two-port demultiplexer. Assuming: di = do = 100 nm, L1 = 628 nm, L2 = 524 nm, G = 16 nm, Si = 0.5 and So = 1, CD = 88 nm
  • [FIG. 11.] (a) Schematic view of the proposed triple-wavelength demultiplexer structure, (b) its transmission spectra for L1 = 508 nm, L2 = 556 nm, L3 = 460 nm, W1 = W2 = W3 = 80 nm, G = 12 nm, di = 48 nm, WD = 80 nm, Si = 1, and So = 0.3. Magnetic field distribution for wavelengths of (c) 1430 nm (d) 1550 nm, and (e) 1310 nm, demonstrate the demultiplexing performance of the device.
    (a) Schematic view of the proposed triple-wavelength demultiplexer structure, (b) its transmission spectra for L1 = 508 nm, L2 = 556 nm, L3 = 460 nm, W1 = W2 = W3 = 80 nm, G = 12 nm, di = 48 nm, WD = 80 nm, Si = 1, and So = 0.3. Magnetic field distribution for wavelengths of (c) 1430 nm (d) 1550 nm, and (e) 1310 nm, demonstrate the demultiplexing performance of the device.